1. Field of the Invention
The present invention relates to an energy output control method for and a circuit of a welding machine, heating apparatus, and a direct current motor, and, more particularly, to a pulse width modulating method for and a circuit of the energy output.
2. Description of the Related Art
A PWM (Pulse Width Modulation) circuit is widely used for controlling the output energy of a welding machine, a switch of a heating apparatus, and a direct current motor used in industry. The conventional PWM uses a high-frequency transformer to accomplish the PWM output energy. When using the high-frequency transformer, an energy output circuit sometimes can not reach a high energy output and constrains the output energy. Using the high-frequency transformer to process the PWM, when a cycle of a pulse is fixed and the frequency keeps in constant, a duty cycle can be modulated by modulating a pulse width to control the output energy. While modulating a bigger range in this case, it would result in a duty is too huge so that the energy output is not stable.